Heat recovery system



Nov. 10, 1936. A. J. EBNER v 2,060,290

HEAT RECOVERY SYSTEM Filed June 22, 1935 2 Sheets-Sheet;

O NV 'r LL.- A d z- N N v N l 1 Qlfreol J. hner BY l 7 j 7 NE'S.'

HEAT RECOVERY SYSTEM Filed June 22, 1955 2 Sheets-Sheet 2 Patented Nov.10, 1936 UNITED STATES PATENT `OFFICE:

2,060,290 HEAT RECOVERY SYSTEM` tion of Maine Application June 2z, 1935,serial Nn. 21,967

17 Claims.

The present invention relates to improvements in heat recovery systems.

It is frequently desirable sin connection with furnaces or the likewhich deliver gases at high L temperature to utilize a part, generally amajor part, of the sensible heat or the latent heatv of the gases forthe purpose of the heating of air Y or other gas or liquids, theproduction of steam, and other uses. Sometimes it is desired to utilizewaste heat gas for use in instrumentalities having an upper limit oftemperature which i's substantially lower than the temperature of thewaste heat gas, or substantially lower than the temperature which can beproduced by the combustion of the waste heat gas. To attempt to heat theinstrumentalities referred to to moderate temperatures directly by wasteheat gases of high temperature introduces diicult problems in controland in protection of the apparatus and in'y safeguarding the substancesbeing heated in said instrumentalities against overheating. Taking anexample from open hearth furnace practice, the brick regeneratorsassociated therewith are not well adapted to low temperature heatexchange, metallic preheaters for air are not well adapted to hightemperature heat exchange, and gas-liquid heat exchangers are bestsuited to temperatures midway of the range between the dischargetemperature at the open hearth and atmospheric temperature. f

In the drawings the means for delivering hig temperature gas take theform of an open hearth furnace or acupola. The means for utilizing theheat units in the hot gas which is best suited for moderate temperaturesis illustrated in the form of a boiler, and the means for utilizing theheat units at the lower temperatures of the gas is illustrated as an airpreheater. As the descrip-- tion proceeds it will be apparent that theinvention is of broader application than is indicated. by the drawings.For example, the means for utilizing theheat units in the moderate rangeof temperatures may take the form of a heater for fuel oil for raisingthe temperature of said fuel oil to better condition it for combustionor other purposes.v Such devices in the description which follows willbe referred to broadly as liquid cooled heatexchangers. Devices forutilizing the heat units of `the waste gas at the lower temperaturesthereof may of course be used for the heatingv of gas other than air; ifpreferred. In the description which follows, mechanism for utilizing theheat units in which the substance to be heated is air or other gas,.suchmeans will be referred to as gas cooled heat exchangers.

In understanding the description which follows 1t 4should be borne inmind that liquid coded heat.

exchangers, by reason of the high heat storage capacity of,-liquid areadapted for heat transfer at temperatures higher than are gas cooledheat exchangers.

An object of the present invention is to utilize waste heat gases in aneflicient manner for the preheating of air or other gas and for the pro-6 duction of steam ,to the end that heat units in the waste gas may beutilized to the best advantage for the required temperature ranges ofthe instrumentalities involved.

A further object is to provide a heat recovery system for effectivelyutilizing hot gases through a greater temperature range than hasheretofore been commercially feasible and tov provide for each part ofsaid temperature range a heat utilizing means most suitable andeconomical for its particular part of said heat range.

A further object is to provide a heat recoveryV system fori hot gases inwhich a portion of the heat of the hot gases is absorbed in liquidcooled means to reduce the temperature of said gases20 to a point wherethey can be passed safely through relatively inexpensive gas cooled heatrecovery means.

A furtherobject is to provide a heat recovery system in which the heatunits are recovered in two different media, means being provided to varythe absorption of heat units by one of saidmedia in order to control theabsorption of heat units-by the other of said media without sacricingtotal heat absorption.

A further object is to provide a heat recovery system for hot gasesincluding a boiler for utilizing heat units in said hot gases in acertain temperature range oiy said gases and having gas cooled heattransfer means for utilizing heat units in a lower temperature range,said system having means to control the distribution of said hot gases,the elements of said system being so disposed as to utilize economicallythe heatunits not utilized in said boiler.

A further object is to provide a heat recovery system for hot gaseshaving means to economically temper hot gases prior to their use in aheat absorbing means, said tempering means being adapted to absorb andutilize a controlled portion of the heat units in the waste heat gasavailable.

A further object is to provide a heat recovery system for recovering`efficiently the heat units in hot gases by means of relativelyinexpensive instrumeritalities.

Further objects will appear as the description proceeds.

Referring to the drawings- Figure 1 is a diagrammatic view illustratingan embodiment of the present invention in which the source of waste heatgas is an open hearth furnace, in the operation of which it is necessaryto preheat air at high temperatures: and

Figure 2 represents another embodiment-of the present inventionutilizing a cupola which does 60 not require a supply of air at the hightemperatures required for an open hearth furnace.

Referring first to Figure 1, the numeral Ill indicates an open hearthfurnace having associated therewith the usual regenerators II and I2.

As will be understood by those skilled in the art, means will beprovided for reversing the regenerators from air to blast or from blastto air. Means for this purpose form no part of the present invention andare not illustrated.

As the parts are shown in Figure 1, the regenerator II is on air, thatis-it is giving up heat to air passing through said regenerator into thefurnace I0, and the regenerator I2 is on blast, that is-it is beingheated up by the hot waste heat gases being delivered through it by theopen hearth furnace I0. The numeral I3 indicates a steam unit connectedto the regenerator which is on blast through the waste gas flue I4. Saidsteam unit includes the boiler I5 and the by-pass duct I6, though, asindicated above, the member I5 may be any liquid cooled heat exchanger.The boiler I5 has been illustrated in the form of' a fire tube boilerhaving its re tubes communicating with the inlet header I1 and with theoutlet header I8. The by-pass du'ct I6 provides a by-pass whereby wasteheat gases may, when desired, be shunted away from the re tubes of thefire tube boiler I5. Said by-pass duct is controlled by the damper I9,which may be controlled by mechanism which will be referred topresently.

The numeral 20 indicates an air preheater having the re tubes 2 I-2Iextending longitudinally thereof. It will be understood that the member20 may be any heat exchanger which is cooled by air or other gas, or, inother words, in which the .substance being heated is air or other gas.Said preheater 20, as illustrated, has the function of preheating theair delivered to the regenerators II and I2 and utilizes a substantialportion of the heat units in the gases whichhave passed through thetubes of the boiler I5 or the by-pass duct I6. The re tubes 2I-2Icommunicate at one end thereof with the header I8 oi the steam unit I3.Said fire tubes 2I communicate at their other ends with the stack 22.The air preheater 20 is provided with the air intake 23 and with the airoutlet duct 24, which duct 24 leads to the regenerator which is on air,that is-as the parts are illustrated in Figure 1, to the regenerator II.Air is forced into the intake 23 by the blower 25 driven by the motor orturbine 26. The waste heat gases which have passed through the tubes 2I-2I of the preheater 20 may be accelerated outwardly of said preheaterand up through the stack 22 by means of a blower 21 propelled by theturbine 21a. A steam pipe 28V is illustrated connected with the boilerI5. Said steam pipe 28 may supply steam for operating the turbine 26 andthe turbine 21a. The damper I9, which controls the by-pass duct I6 ofthe steam'unit I3, may be controlled by certain damper regulatingmechanism, indicated as a whole by the numeraljil. The regulatingmechanism 29 maybe responsive to a thermocouple 30 located in the outletheader I8 of the steam drum I3 or to a thermo-couple 3I located in theoutlet duct 24'leading from the air preheater 20, or the regulatingmechanism 29 may be conjointly responsive to both the thermocouple 30and the thermo-couple 3I. In other words, the regulating mechanism 29may, for example, be under the control of the thermocouple 3l unless anduntil the gases in the headerv I8 are too hot for the gas-cooled heatexchanger 20, in which case the thermo-couple 30 will control theregulating mechanism 29 to cause closing movement of the damper I9,whereby more of the hot gases will be directed through and have theirheat absorbed by the boiler I5. Mechanism suitable for the purpose forcontrolling the damper I9 in response to either the temperature in theheader I8 or the duct 24, or both, is readily obtainable in the openmarket and need not be described herein. As an alternative, the boilerI5 may be provided with the steam gauge 3Ia, which, through the cable3Ib, controls the regulating mechanism 29. Said gauge 3Ia will controlthe damper I9 to maintain constant steam functions at the boilerregardless of steam delivery therefrom. Said gauge may be a pressuregauge or flow gauge, or other gauge. The numeral 3Ic indicates apressure gauge responsive to pressure within the furnace I0. Said gauge3Ic, throughl the cable 3| d, controls the turbine 21a. to maintainconstant draft upon the furnace I0.

Referring now to Figure 2, the numeral 32 indicates a cupola whichdelivers combustible waste heat gas. Communicating with the cupola 32 isthe waste gas fue 33 which leads to the combustion chamber 34 formingpart of a steam unit 35. Said steam unit 35 includes the fire tubeboiler 36, the tubes of which at one end have communication with thecombustion chamber 34 and at the other end have communication with theoutlet header 31. The numeral 38 indicates a by-pass duct communicatingwith the combustion chamber 34 and the outlet header 31 whereby productsof combustion from the combustion chamber 34 may be shunted around thetubes of the boiler 36. The by-pass effect of the duct 38 may becontrolled by means of the damper 39, which [is responsive to mechanismto be referred to presently.

Communicating with the outlet header 31 of the steam unit 35 is the airheater 40, which includes a plurality of gas tubes 4I-4I. Said gas tubes4I communicate at one end with the outlet header 31 of the steam unit 35and at the other ends communicate with the stack 42. Gases from thetubes 4I-4I of the air heater 40 may be accelerated up through the stackby means of a blower 43 driven by the motor 43a.

The numeral 44 indicates an air duct supplied by a blower 45 driven bythe motor 46. Said air duct delivers air to the air Aheater 40, whichair ows past the gas tubes 4I, being heated in its passage, and isdelivered from the air heater through the hot air flue 41, whichdelivers heated air to the cupola 32.

'I'he damper 39 in the by-pass 38 of. the steam unit 35 is controlled byregulating mechanism /indicated as a whole by the numeral 48. Saidregulatingmechanism 48 may be controlled by a thermo-couple 49 locatedin the outlet header 31 of the steamvunit 35, or by the thermo-couple 50located in the hot air ue 41; or, said regulating mechanism 48 may,becontrolled conjointly by both of said thermo-couples, similarly to theaction of the thermo-couples 30 and 3| above described. Controlmechanism suitable'for controlling the damper 39 in response totemperature' changes in the header 31, the hot air flue 41, orconjointly inl response to temperature changes in said header 31 andtheflue 41 may. be readily purchased in the open lmarket and need not bedescribed herein. As an alternative, the boiler may be provided with thesteam gauge li, which through the cable. i2, controls the regulatingmechanism 4I. Said gauge il, which may be responsive to steam pressure,steam ilow or vother function of the boiler or other liquid cooled heatexchanger 36, will control the damper 39 to maintain constant functionsat the boiler.

'Ihe mode of operation of each of the described embodiments of thepresent invention will be in the drawings).

example, approximately 2600 deg. F. to 1400 deg.

F. The hot gases then enter the steam unit i3, which still furtherreduces the temperature of the gases .to perhaps 900 deg. F. Said hotgases then enter the air preheater 2li, which further reduces theirtemperatures to about 250 deg. F. 'I'he hot gases at this reducedtemperature then pass to the stack' 22.

The combustion'air for the open hearth furnace III is delivered from theatmosphere at, for example, 'I0 deg. F. to the air preheater 2li, beingdischarged therefromA into the hot air duct 24 at a temperatureapproaching 900 deg.- F. ,This air then. passes to the regenerator whichis on air (indicated as regenerator Il in the drawings),-

where the combustion air is further raised to a temperature of say 2000deg. F. Water may be delivered to the boiler II at a temperature of 200deg- F. and may attain a steam temperature of perhaps 350 deg. F.v

The above figures are merely illustrative nd should not be considered ina limiting sense. aid figures have been recited merely to show that-there isa good differential between the waste gas temperature and the.temperature of the medium being heated. Inasmuch as the air preheater20 will ordinari be made of metal, the temperatures attained in.

said air preheater are suitable therefor, so that the use of expensivealloys for resistance to high temperatures is not required in thispreheater.

Reference will now be made to the by-pass duct Il, which may becontrolled by the damper i9. Bycontrolling the by-pass of waste heatgases around the boiler I5, the temperature in the header la and/r inrthe not air duct u may be controlled. As indicated above, the damper I 9may be controlled either in response-to the hot air being deliveredthrough .the duct 24, or lin response to temperatures of the waste heatgases about to enter the preheater 20, or the control may be aconjointone whereby to hold substantially'constant the temperature ofthe air in the air duct 24 unless and until the gases about to enter thetubesI 2l of the air preheater get too hot, at which time thethermo-couple 30 will cause closing movement of the damper I9, therebycausing the boiler I5 to absorb a greater porizlon of the heat units andthereby save the air heater 20 from the action of. gases at destructivetemperatures. Expressed in other language, the damper I9 is controlledin response to temperature functions of the preheater 20, that ls-eitherin response to temperature changes in the hot controlled by the steamgauze Ila to maintain constant functions at the boiler I5.

The mode of operation of the structure shown in Figure 2 requires onlybrief explanation. In this case the waste heat gases are combustible andare burned in the combustion chamber 34. Figure 2 is illustrative of aconstruction in which only a moderate degree of .air preheat is desired.According to this construction, the damper I! may be regulated inresponse to temperatures within the header 31 or within the hot air ilue4l, or it may be controlled conjointly according to the temperatureswithin said instrumentalities, similarly to the actionl of the damperI9, described above, or said damper 39 may be controlled to maintainconstant functions at the boiler, similarly to the action'of the steamgauge 3Ia, described above.

Though certain embodiments of the present invention have been describedmore or less in detail, it will be understood that many modificationswill occur to those skilled in the art. It is intended to cover all suchmodifications that fall' within the scope of the appended claims.

What is claimed is- 1. In a heat recovery system, in combination, meansfor delivering gases containing heat umts, a liquid cooled heatexchanger adapted and positioned lto utilize a. portion of said heatunits, a gas cooled heat exchanger for delivering gaseous medium to saidgas delivery means, said gas cooled heat exchanger being positioned toreceive heat units which have passed through said liquid cooled heatexchanger, said liquid cooled heat exchanger having a by-pass inparallel therewith, and means for regulating said by-pass in response toconditions at said gas cooled heat exchangen 2. In a heat recoverysystem, in combination, means for delivering gas having heat unitstherein, a liquid cooled heat exchanger connected to said gas.delivering means to utilize a portiona of the heat units in said gas, agas cooled heat exchanger connected to said gas delivering means fordelivering heated gaseous medium thereto,y

said gas cooled heat exchanger being positioned to receive gases whichhave given up a portion of their heat units to said liquid cooled heatexchanger, a shunt passage around said liquid cooled heat exchanger, andmeans for throttling Asaid shunt passage, said throttling means beingresponsive to conditions controlling the temperature of gaseous mediumdeliveredI to said gas delivering means. l

3. In a heat recovery system, in combination, a liquid cooled heatexchanger and a gas cooled heat exchanger connected in series for there-` ception of hot gases, a shunt passageway around said liquid cooledheat exchanger, damper means for controlling said passageway, and meansfor controlling said damper means responsive to functionsof said gascooled heat exchanger.

4. In a. heat-recovery system, in combination, a liquid cooled heatexchanger and a gas cooled heat exchanger connected in series for thereception of hot gases, a shunt passageway around said liquid cooledheat exchanger, damper means for controlling said passageway, and meansvfor controlling saiddamperresponsive to temperature functions of saidgas cooled heat exchanger.

5. In a heat recovery system, in combination, means for delivering gascontaining heat umts, a liquid cooled heat exchanger for utilizingf'theheat units in said gas. a gas cooled heat exchanger in series with saidliquid cooled heat exchanger, and means responsive to conditions at saidgas cooled heat exchanger for controlling the division of heat unitsutilized in said liquid cooled heat exchanger and in said gas cooledheat exchanger.

6. In a heat recovery system, in combination, means for delivering gascontaining heat units, a liquid cooled heat exchanger for utilizing theheat units in said gas, a gas cooled heat exchanger in series with saidliquid cooled heat exchanger, a by-pass duct around said liquid cooledheat exchanger, and damper means in said duct for controlling thedivision of heat units utilized in said heat exchangers, said dampermeans being responsive to the temperature of gas heated by said gascooled heat exchanger.

7. In a heat recovery system, in combination, means for delivering gascontaining heat units, a liquid cooled heat exchanger for utilizing theheat units in said gas, a gas cooled heat exchanger in series with saidliquid cooled heat exchanger, a by-pass duct around said liquid cooledheat exchanger, damper means in said duct for controlling the divisionof heat units utilized in said heat exchangers, and means forcontrolling .said damper responsive to the temperature of gases enteringsaid gas cooled heat exchanger.

8. In a heat recovery system, in combination, means Vfor delivering gascontaining heat units, a liquid cooled heat exchanger for utilizing theheat units in said gas, a gas cooled heat exchanger in series with saidliquid cooled heat exchanger, a by-pass duct around said liquidcooledheat exchanger, damper means in said duct for controlling thedivision of heat units utilized in said heat exchangers, and means forcontrolling said damper conjointly responsive to the heated gasdelivered by said gas cooled heat exchanger and to the gases enteringsaid gas cooled heat exchanger.

9. In combination, an open hearth furnace, a pair of regeneratorsoperatively connected thereto, a waste heat boiler adapted to beconnected to one of said regenerators, an air preheater connected inseries with said boiler, a hot air duct for conducting heated air fromsaid preheater to the other of said regenerators, a bypass around saidboiler, a damper in said bypass, and means for controlling said damperresponsive to heat conditions in said system beyond said boiler.

10. I combination, an open hearth furnace, a pair of regeneratorsoperatively connected thereto, a waste heat boiler adapted to beconnected to one of said regenerators, an air preheater connected inseries with said boiler, a hot air duct for conducting heated air fromsaid preheater to the other of said regenerators, a by-pass around saidboiler, a damper in said by-pass, a gauge responsive to functions ofsaid boiler, and means for controlling said damper responsive to saidgauge.

11. In combination, an open hearth furnace, a pair of regeneratorsoperatively connected thereto, a waste heat boiler adapted to beconnected to one of said regenerators, an air preheater connected inseries with said boiler, a hot air duct for conducting hot air from saidpreheater to the other of said regenerators, a by-pass around saidboiler, a damper in said by-pass, and means for controlling said damperinresponse to the temperature within said hot air'duct.

12. In combination, an open hearth furnace, a pair of yregz'aneratorsoperatively connected thereto, a waste heat boiler adapted to beconnecter. to one of said regenerators, an air preheater connected inseries with said boiler, a hot air duct for conducting hot air from saidpreheater to the other of said regenerators, a by-pass around saidboiler, a damper in said by-pass, and means for controlling said damperin response to the temperature of hot gases entering said air preheater.

13. In combination, an open hearth furnace, a pair of regeneratorsoperatively connected thereto, a waste heat boiler adapted to beconnected to one of said regenerators, an air preheater connected inseries with said boiler, a hot air duct for conducting hot air from said'preheater to the other of said regenerators, a by-pass around saidboiler, a damper in said by-pass, and means for controlling said damperconjointly responsive to the temperature of air within said air ductandto the temperature of gases entering said preheater.

14. In combination, means for delivering a combustible gas, a boilerhaving a combustion chamber associated therewith for burning saidcombustible gas, an air preheater for receiving products of combustionfrom said combustion chamber after said products of combustion havegiven up part of their heat units to said boiler, a by-pass around saidboiler, and means responsive to conditions at said air preheater forcontrolling said by-pass to control the division of heat units in saidproducts of combustion utilized by said boiler and said preheater.

15. In combination, means for delivering a combustible gas, a boilerhaving a combustion chamber associated .therewith for burning saidcombustible gas, an air preheater for receiving products of combustionfrom said combustion chamber after said products of combustion havegiven up part of their heat units to said boiler, a by-pass around saidboiler, and means for controlling said by-pass to control the divisionof heat units in said products of combustion utilized by said boiler andsaid preheater, said controlling means being responsive to thetemperature of the air delivered by said preheater.

16. In combination, means for delivering a combustible gas, a boilerhaving a combustion chamber associated therewith for burning saidcombustible gas, an air preheater for receiving products of combustionfrom said combustion chamber after said products of vcombustion havegiven up part of their heat units to said boiler, a by-pass around saidboiler, and means for controlling said by-pass to control the divisionof heat units in said products of combustion utilized by said boiler andsaid preheater, said controlling means being responsive to thetemperature of gas entering said preheater.

17. In combination, means for delivering a combustible gas, a boilerhaving a combustion chamber associated therewith for burning saidcombustible gas, an air preheater for receiving products of combustionfrom said combustion chamber after said products of combustion havegiven up part of their heat units to said boiler, a by-pass around saidboiler, and means for controlling said by-pass to control the divisionof heat units in said products of combustion utilized by said boiler andsaid preheater,l said controlling means being conjointly responsive tothe temperature of the air delivered by said air preheater and to thetemperature of gas entering said air preheater.

ALFRED J. EBN ER.

